This invention relates to a member for separating mixed gases in a concentrated form by utilizing differences in the rates of permeation of the gases through a film and to a method for the manufacture of the gas separating member.
Searches are now under way for methods of separating oxygen and nitrogen from air and obtaining air rich in oxygen, methods of evacuating a room of excess carbon dioxide gas and ensuring the necessary oxygen supply for the room, and methods for separating hydrogen in a concentrated form from various hydrogen-containing mixed gases emanating from various manufacturing processes and permitting disposal of gas by-products entrained by the mixed gases. It is highly important that these processes of gas separation should be effected without consuming extra energy.
Various methods are available to carry out such gas separation, including absorption, adsorption, diffusion, and deep-freeze separation. From the energy-saving point of view, a diffusion method which makes effective use of film separation techniques holds great promise. However, the separating members developed to date possess low gas separation factors or exhibit low degrees of permeability to gases and therefore have found practical utility only in limited applications.
The inventors have disclosed in U.S. Pat. No. 4,410,338 a novel gas separating member which outperforms the conventional gas separating members in gas separation capacity and permeability to gas and enjoys high mechanical strength, and a method for manufacture of the gas separating member. The gas separating member so disclosed undeniably outperforms the conventional counter-types in terms of gas separation capacity and permeability to gas. As viewed from the energy-saving point of view, however, it has room for further improvement.
Empirically, it has been found that a film of high gas separation capacity cannot easily be improved in permeability to gas and a film of high permeability to gas has low gas separation capacity. It has been an extremely difficult task, therefore, to improve a given gas separating member in both gas separation capacity and permeability to gas. As a material intended for the solution of this problem, a gas separating member incorporating at least two polymer films has been proposed (Japanese Patent Application Laid-open Number 1982/30528). This gas separating member has the drawback that, under certain mechanical or thermal conditions, the first and second layers thereof may separate from each other. This layer separation may result in serious impairment of the performance of the film separating material.